This invention relates to a new and unique inbred tetraploid watermelon line, designated 4XASSS4.
Watermelon is an important horticultural crop that accounts for 2% of the world area devoted to vegetable crops. There were 3,810,535 Ha of watermelon grown in the world and 51,110 Ha of watermelons grown in the United States in 2009. Asia is by far the most important watermelon production site with 78% of the world area and 83.4% of the world production of 100,687,056 metric tones (FAOSTAT|© FAO Statistics Division 2011|20 Feb. 2011; http://faostat.fao.org/site/291/default.aspx). The estimated annual world watermelon value exceeded $7.6 billion when using the United States average price for 1995-1997. Watermelon is grown in forty-four states in the USA, with Florida, Georgia, California, and Texas, having long warm growing seasons, being the major producing states. In the U.S., watermelon production has increased from 1.2 M tons in 1980 to 3.8 M tons in 2009, with an annual farm value of $470 million (U.S. Department of Agriculture, Agricultural Statistics, 2009). In recent years, there has been an increase in consumer demand for seedless watermelons and production of seedless watermelon has increased significantly. Today, over 80% of the watermelons produced in the United States are triploid seedless watermelons (U.S. National Watermelon Promotion Board; www.watermelon.org). Seedless watermelon receives well above the average price for seeded watermelons in the market. Triploid seedless watermelon also produces higher yields than the diploid seeded watermelons.
Triploid seedless watermelon is a true F1 hybrid between a tetraploid watermelon, as the female parent, and a diploid watermelon, as the male parent (Kihara, H. 1951, Triploid Watermelons, Proceedings of American Society for Horticultural Science, 58:217-230). Regular watermelons, the seeded diploid watermelons, have 22 chromosomes (2N=2X=22) in their somatic cells. The tetraploid watermelons have 44 chromosomes (2N=4X=44) in their somatic cells. When female flowers of tetraploid plants are crossed pollinated by the male flowers of normal diploid plants, the seeds produced in the fruit of tetraploid plants are triploid seeds. Triploid seeds produce triploid plants. When the triploids plants are grown with the normal diploid plants in the same field, the triploid plants produce fruits that are seedless. The seedless condition in triploid watermelon is the result of the presence of three homologous sets of chromosome per somatic cell rather than the usual two. Cells with three sets of homologous chromosomes are said to be triploid and are designated as 3X. The triploid seedless watermelons have 33 chromosomes (2N=3X=33) in their somatic cells. The inability of the triploid zygote to produce normal viable gametes (pollen and egg cells) causes the absence of seeds in triploid fruits. Typically, seedless watermelons contain small edible white ovules, similar to those in immature cucumbers.
Triploid seedless watermelons have been commercially grown in the United States since the late 1980's. The popularity of seedless watermelon has increased since its commercial introduction in the United States. Most of the watermelons produced in California in 2010 were triploid seedless watermelons. Triploid varieties produce higher yields than the diploid seeded varieties, due to more fruit per plant and longer harvest period. The triploid seedless watermelon receives premium prices because of the high quality flesh virtually free of seeds.